Photo Quiz

Asymptomatic Yellowish Papules

Am Fam Physician. 2006 Sep 1;74(5):807-810.

A 39-year-old woman presented with a rash on her neck and arms. The rash was not pruritic or painful. She was otherwise asymptomatic and had no significant medical or family history. On physical examination, confluent yellowish papules and plaques were noted in a cobblestone pattern on her lateral neck and bilateral antecubital fossae (see accompanying figure). The patient stated that the rash had been present as early as nine years of age.

Question

Based on the patient’s history and physical examination, which one of the following is the most likely diagnosis?

A. Eruptive xanthoma.

B. Toxicity from saltpeter (potassium nitrate) exposure.

C. Pseudoxanthoma elasticum.

D. Penicillamine (Cuprimine) therapy.

E. Cutis laxa.

Discussion

The answer is C: pseudoxanthoma elasticum. Pseudoxanthoma elasticum is a genetic defect of elastic tissue that manifests as dystrophic calcification of elastic fibers within the dermis, retina, and internal elastic lamina of medium-sized arteries. On the skin, pseudoxanthoma elasticum presents with multiple yellowish papules and plaques arranged in a cobblestone pattern resembling “plucked chicken skin.” The skin exhibits decreased elasticity and increased laxity. It typically involves the flexural surface of the neck and axillae, as well as antecubital and popliteal fossae. Inguinal, periumbilical, oral, rectal, and vaginal areas are involved less commonly. Occasionally, patients will not have any skin lesions.

Pseudoxanthoma elasticum produces ocular changes consisting of angioid streaks. These represent tears in Bruch’s membrane from weakening of calcified elastic fibers. The funduscopic examination reveals broad, irregular lines on the retina that are red-brown to gray. Angioid streaks also may occur with various clinical conditions including Ehlers-Danlos syndrome, sickle cell disease, and Paget’s disease.1

Pseudoxanthoma elasticum is inherited primarily in an autosomal recessive fashion.2 The estimated prevalence ranges from one in 70,000 to one in 100,000 persons, with a female-to-male ratio of 2:1.3,4 There is an average delay of nine years from initial presentation of skin lesions to diagnosis.1 Definitive diagnosis is established by performing a skin biopsy. Histopathologic changes reveal a fragmented appearance of curled and split, calcified elastic fibers.

Genetic counseling for patients with pseudoxanthoma elasticum and their families should be offered. First-degree relatives of patients with pseudoxanthoma elasticum should be screened with a thorough skin examination and dilated funduscopic examination. Dermatology consultation may be helpful. Effects of pseudoxanthoma elasticum on pregnancy are variable. Many women with pseudoxanthoma elasticum have uncomplicated pregnancies with the delivery of a healthy infant.6

Most forms of xanthoma present as a group of discrete, yellowish papules that are firm to palpation. Examples include xanthelasma and eruptive xanthomas. Eruptive xanthomas tend to occur on the buttocks and extensor aspects of the elbows and knees. They almost always are associated with an underlying familial cholesterol disorder and resolve with treatment of the dyslipoproteinemia.

Saltpeter is a form of potassium nitrate most commonly used as a fertilizer. Exposure can produce skin lesions identical to those of pseudoxanthoma elasticum; typically, the lesions are considered to be an exogenous, acquired form of the disease.7 Reported cases generally occur in adult men working in agriculture.

Long-term therapy with penicillamine has been found to produce elastolytic changes similar to those of pseudoxanthoma elasticum.8 Most reported cases have occurred in patients treated for Wilson’s disease.

Cutis laxa is a congenital disorder of elastic tissue resulting in loose, redundant folds of skin. It is most common in infants, but an acquired form can affect children and adults. Although skin laxity is present in cutis laxa and pseudoxanthoma elasticum, yellowish papules in a cobblestone pattern are not characteristic of cutis laxa.

The opinions and assertions contained herein are the private views of the authors and are not to be construed as official or as reflecting the views of the U.S. Air Force Medical Corps or the U.S. Air Force at large.

Information on pseudoxanthoma elasticum and related support groups is available from the Web sites of PXE International (http://www.pxe.org) and the National Association for Pseudoxanthoma Elasticum (http://www.napxe.org).

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